I am shopping for a new aluminum rad for the XK140 roadster. The past threads on this subject seem to be old. The issue is - which one to purchase? They all seem to look about the same and to be made about the same way, but there is variation in the price. There are ones from CJs, XKs, Welsh, Terry’s, Ron Davis, and Wizardcooling, with the latter having the best price by $200. In general, I don’t like to purchase items without testimonials of people who have actually used the item. However, in this case I have only one personal recommendation. If any members that have purchased and used radiators from any of the companies could offer comments, it would be appreciated.
I bought one from Wizardcooling recently. I don’t like the looks of the top of it, particularly their advertising cut right into the metal. Otherwise the construction looks good. Still hard to get past the most visible part looks wrong.
best but not the cheapest…that sounds normal…is NAR radiator from England.
Looks just like original and can use the original radiator cap as well.
they will also powder coat it satin black and send it anywhere.
120 radiator as example…
Art. Thanks for this information. I thought by the photo that there was
something different on the top where the cap goes, but couldn’t make it
out. I agree for $1000 a rad should both function well and look good.
Thanks again for your reply. Don
Wow. That is a beauty. Thanks for sharing. Do you mean that most or some of the rads don’t use the original cap? Is this a problem?
I think the funny cap is a “truck cap” used on 120/7. 140s had a normal cap. But they had two forms so the early one may be like 120. I am not sure if powder coating or even paint might resist heat transfer. Probably worth considering with these cars having a slim margin in normal use. Today traffic is a lot heavier than it was when I drove mine in the late sixties.
True words Art. The ones I see in the US are not painted. If that car is
in England with its cool weather, the paint or coating is probably fine.
For me in Florida it won’t be painted. I am in a kind of a rural area
north of Tampa and I get nervous driving the XK in much traffic. Too many
dangerous drivers not watching what they are doing or some of them
tail-gating to get a closer look. I like to go our early on Sat or Sun
morning for a cruise on the rural roads. Much more enjoyable without
stress. The car, the road, the wind, freedom - to me this is the real
enjoyment I get with have a very special classic car.
Attached are some photos of a few of the cars I am fortunate enough to own
Regarding painting an aluminium radiator, it is my professional experience that painting aluminium parts (castings, sheet-metal constructions) will definitely improve heat dissipation.The exact color choice has lesser influence but black has the highest radiation factor. So there was a reason why car manufacturers painted their radiators black. A thin layer will do the job.
Bob K.
Bob. Thanks for the message. This is very interesting. I have no
experience in field, but it seems counter-intuitive that a coating, even
thin, on the top of metal would help dissipate heat from inside the
container. Can you offer any technical explanation why this is so?
Additionally, if I am not mistaken, I think on most modern cars the
aluminum rads and condensers are not painted.
Thanks, Don
I bought mine in january at serck in UK : http://www.serckservicesmotorsport.co.uk/p0/jaguar/187516.htm
It’s not painted, it’s 450£ w/o vat and i’m very happy so far. I did a 900km trip last week end and never exceeded 85°.
the cap is not funny…that’s a proper XK120 cap. 4# cap…all XK120’s had this cap.
and the powder coat is simply an option.
only a question if you want your car to look as good and original as it runs or do you only care about performance.
the top of the radiator is also an aluminum pressing and not pieces welded together with welds showing.
Don,
It’s a long time ago that I dealt with the subject, but I’ll give it a try.
The heat dissipation from the radiator is (apart from the air velocity trough the radiator) depending of the combined heat transfer from (1) the cooling fluid in contact with the inner radiator wall, (2) the thermal conductivity of the material of the radiator and (3) the convection combined with (4) radiation of the outer surface of the radiator into the surrounding air.
It’s the radiation (aspect 4) that has an important impact on the final step in transferring heat to air. A lacquered aluminium surface has a “emissivity” that is at least 10 times better than the emissivity of (untreated) aluminium. Polished aluminium is even (much) worse. It would then even be better to have a somewhat oxidized material.
As a “rule of thumb” I remember that the temperature of an internally heated (non-lacquered) aluminium “box” will drop by 10% when it is painted. This is of course. also valid for an engine.
So your intuitive reaction deals with the conductive aspect of the heat transfer through the aluminium + additional layer of paint and you’re right that the conduction will be somewhat lower, but this is more than compensated by the favorable radiation/emission aspect of the total heat dissipation.
Hope this helps.
Regards,
Bob
.
To add to Bob,
Black has the highest emmisivity, white the lowest. That is why roofs in the tropics are white, and in cold climes dark colors.
Anyone remember the “black body” from physics class ? Anyone … anyone…anyone.
Karl
Wow Bob. That is a great explanation to an non-chemist, non-engineer. And
I even got to learn a new word - “emissivity.”
Thanks for taking the time to dig this up again.
Don
Radiators have paint coatings for a variety of reasons. The color of paint is not too important (black is better radiator on average than white, emissivities of non-metallic black paints are around 0.9 and white paints around 0.7, so black will work enough better to notice) but paint is important for radiation. The outer coat of the paint is what matters most. The paint layer does very little insulation but increases the emissivity substantially above bare metal.
Radiators tend to have about 2/3 of their thermal transfer by convection to the flowing air (hence the fan for when the car is moving slowly) and about 1/3 possible by blackbody radiation. Bare metals can reduce that 33% radiation portion by half or more, metallic paints can be in between. Non-metallic paints and varnishes are used quite a bit. Household radiators commonly are white and car radiators commonly are black, due in part to aesthetic choices.
I think another factor is the rate of flow of water past the cooling surface . One of the reasons the cars have a thermostat
And a reason why removing it doesn’t necessarily improve cooling .
What kinds of paint will be beneficial? Does this imply a thicker coat is more effective than a thinner coat? Do we still need a special base coat over aluminum? I think zinc chromate was always considered a required base paint for aluminum. Powder coating was mentioned earlier. It may be a kind of paint in itself but are it’s properties suitable?
Art,
As far as I know, all synthetic paints are OK as long as they don’t contain any metallic parts: so no metallic paints. Pre-treatment of the metal (only a couple of microns thick!) doesn’t really affect the thermal behavior.
It is not the thickness of the lacquer layer that determines the emissivity value: it’s the outer lacquer surface itself! So the thickness should just be sufficient to obtain a certain corrosion resistance over life.
Bob K.
To better answer Don’s original question here are a few shots of the actual unit in it’s naked form.
Thanks Art. Its nice looking, but I agree would be better without the
Wizard monogram on it. I’ve order the rad yesterday from SNG and it is
coming from GB. The price was the best. I am kind of surprised at how
competitive the prices are for the British made products, but I supposed
the currency value has a lot to do with it. I got the rad with the fan
attached that will replace the stock pully fan. As I am not converting to
an alternator, I was concerned that it would pull too many amps but was
advised that it uses 8 amps so that should be fine.
Thank you everyone for the discussion on the aluminum radiators and
painting them. I learned a lot from the discussion.
The member of this forum provide a great source of information and wisdom.